1. Field of The Invention
This invention relates to the art of additives for organosiloxane composition and more particularly, to a method for preparing an organosilicon group-bearing cyclic isocyanuric ester in high efficiency. The ester is very useful as an accelerator or promotor for adhesion of room temperature vulcanizable organosiloxane compositions or an additive for organosiloxane compositions suitable for fiber treatment.
2. Description of the Prior Art
For the production of an organosilicon group-containing isocyanuric ester, there is known a process in which hydrogen silane is added to the allyl group of allyl isocyanurate in the presence of a catalyst such as platinum, rhodium or the like. This process is described in French Patent No. 1,579,902. However, this process requires a large amount of the catalyst because the isocyanuric acid ring serves as an inhibitor for the addition reaction. In addition, a one molecule-addition product and a two molecule-addition product are secondarily formed, thus making it difficult to obtain a three molecule-addition product or trimer alone.
U.S. Pat. No. 3,598,852 describes a process of the cyclic isocyanuric ester in which chloropropyl silane (.dbd.Si(CH.sub.2).sub.3 Cl) and potassium cyanate (KOCN) are reacted in a polar solvent such as dimethylformamide. This process essentially requires the use of the polar solvent, which, in turn, requires removal of the solvent so as to purify an intended product. However, complete removal of the polar solvent even by vacuum stripping will be difficult.